Semiconductor device and method for manufacturing semiconductor device

ABSTRACT

Provided are a semiconductor device in which abrasive grain marks are formed in a surface of a semiconductor substrate, a dopant diffusion region has a portion extending in a direction which forms an angle included in a range of −5° to +5° with a direction in which the abrasive grain marks extend, and the dopant diffusion region is formed by diffusing a dopant from a doping paste placed on one surface of the semiconductor substrate; and a method for manufacturing the semiconductor device.

TECHNICAL FIELD

The present invention relates to a semiconductor device and a method formanufacturing a semiconductor device.

BACKGROUND ART

In recent years, development of clean energy has been desired due to theproblem of exhaustion of energy resources, global environmental problemssuch as an increase in CO₂ in the atmosphere, and the like, andphotovoltaic power generation using solar cells in particular amongsemiconductor devices has been developed, put to practical use, and isprogressing as a new energy source.

As a solar cell, a bifacial electrode type solar cell has beenconventionally a mainstream, in which a p-n junction is formed forexample by diffusing an impurity having a conductivity type opposite tothat of a single crystal or polycrystalline silicon substrate, into alight receiving surface of the silicon substrate, and electrodes arerespectively formed on the light receiving surface and a back surfaceopposite to the light receiving surface of the silicon substrate.Further, in the bifacial electrode type solar cell, it is also common toachieve higher output using a back surface field effect, by diffusing ahigh concentration of an impurity having the same conductivity type asthat of the silicon substrate into the back surface of the siliconsubstrate.

In addition, research and development have also been made for a backelectrode type solar cell in which no electrode is formed on a lightreceiving surface of a silicon substrate and electrodes are formed onlyon a back surface of the silicon substrate (see, for example, PTD 1(Japanese Patent Laying-Open No. 2006-156646) and the like).

Hereinafter, one example of a method for manufacturing a conventionalback electrode type solar cell will be described with reference to theschematic cross sectional views of FIGS. 30( a) to 30(i).

First, as shown in FIG. 30( a), an n-type doping paste 103 is applied ona back surface of a silicon substrate 101 having an n-type or p-typeconductivity type, and dried. N-type doping paste 103 is pattern-appliedto follow the desired shape of an n-type dopant diffusion region.

Here, as silicon substrate 101, for example, a silicon substrateobtained by slicing a silicon ingot can be used. Further, as siliconsubstrate 101, it is desirable to use a silicon substrate from which aslice damage layer caused by slicing has been removed. It is noted thatthe slice damage layer can be removed, for example, by etching with amixed acid of an aqueous solution of hydrogen fluoride and nitric acid.

It is noted that the surface having n-type doping paste 103 appliedthereon is described here as the back surface of silicon substrate 101,and the other surface of silicon substrate 101 serves as a lightreceiving surface of the solar cell. Hereinafter, the light receivingsurface may be referred to as a front surface.

Next, as shown in FIG. 30( b), an n-type dopant is diffused from n-typedoping paste 103 into semiconductor substrate 101 to form an n-typedopant diffusion region 113. Thereafter, a residue of n-type dopingpaste 103 on the back surface of silicon substrate 101 is removed withan aqueous solution of hydrogen fluoride.

Next, as shown in FIG. 30( c), a p-type doping paste 104 ispattern-applied on the back surface of silicon substrate 101 to followthe desired shape of a p-type dopant diffusion region, and dried.

Next, as shown in FIG. 30( d), a p-type dopant is diffused from p-typedoping paste 104 into silicon substrate 101 to form a p-type dopantdiffusion region 114, and a residue of p-type doping paste 104 isremoved with an aqueous solution of hydrogen fluoride.

Next, as shown in FIG. 30( e), a silicon oxide film 105 is formed on theback surface of silicon substrate 101 using a CVD method. On thisoccasion, a silicon nitride film, or a laminated film of a silicon oxidefilm and a silicon nitride film may be used instead of silicon oxidefilm 105.

Next, as shown in FIG. 30( f), a texture structure 110 is formed in thefront surface of silicon substrate 101, using for example a mixed acidof an aqueous solution of hydrogen fluoride and nitric acid, or thelike. It is noted that, on this occasion, silicon oxide film 105 on theback surface of silicon substrate 101 serves as a protective mask whentexture structure 110 is formed, and also serves as a passivation filmon the back surface of silicon substrate 101.

Next, as shown in FIG. 30( g), a light receiving surface passivationfilm 106 is formed on the front surface of silicon substrate 101 usingthe CVD method. As light receiving surface passivation film 106, asilicon oxide film, a silicon nitride film, or a laminated film of asilicon oxide film and a silicon nitride film may be used. Further,light receiving surface passivation film 106 is a film also serving as aso-called antireflection film.

Next, as shown in FIG. 30( h), portions of silicon oxide film 105 areremoved to form contact holes 123, 124 which expose portions of thediffusion regions. To form the contact holes, for example, a knownetching paste can be used.

Next, as shown in FIG. 30( i), an electrode for n type 133 electricallyconnected to n-type dopant diffusion region 113 through contact hole 123is formed, and an electrode for p type 134 electrically connected top-type dopant diffusion region 114 through contact hole 124 is formed.

Electrode for n type 133 and electrode for p type 134 can be formed, forexample, by printing a known metal paste by a screen printing method andfiring the metal paste.

CITATION LIST Patent Document

PTD 1: Japanese Patent Laying-Open No. 2006-156646

SUMMARY OF INVENTION Technical Problem

However, the conventional back electrode type solar cell has a problemthat n-type dopant diffusion region 113 and p-type dopant diffusionregion 114 cannot be formed at predetermined regions, respectively, andgood characteristics cannot be obtained stably.

Such a problem occurs not only in the back electrode type solar cell,but also in all semiconductor devices including a solar cell such as abifacial electrode type solar cell.

In view of the above circumstances, one object of the present inventionis to provide a semiconductor device and a method for manufacturing asemiconductor device capable of stably obtaining good characteristics.

Solution to Problem

The present invention is directed to a semiconductor device including asemiconductor substrate, and a dopant diffusion region provided in onesurface of the semiconductor substrate, wherein abrasive grain marks areformed in the surface of the semiconductor substrate, the dopantdiffusion region has a portion extending in a direction which forms anangle included in a range of −5° to +5° with a direction in which theabrasive grain marks extend, and the dopant diffusion region is formedby diffusing a dopant from a doping paste placed on the one surface ofthe semiconductor substrate.

Preferably, in the semiconductor device in accordance with the presentinvention, the dopant diffusion region has at least one of an n-typedopant diffusion region and a p-type dopant diffusion region, and thesemiconductor device further includes an electrode for n type providedon the n-type dopant diffusion region, and an electrode for p typeprovided on the p-type dopant diffusion region.

Further, the present invention is directed to a method for manufacturinga semiconductor device, including the steps of forming abrasive grainmarks extending in one direction in a surface of a semiconductorsubstrate, placing a doping paste having a portion extending in adirection which forms an angle included in a range of −5° to +5° with adirection in which the abrasive grain marks extend, on a portion of thesurface of the semiconductor substrate, and forming a dopant diffusionregion from a dopant in the doping paste on the semiconductor substrate.

Preferably, in the method for manufacturing a semiconductor device inaccordance with the present invention, the step of forming the abrasivegrain marks includes the step of cutting a semiconductor crystal ingotwith a wire saw.

Further, preferably, the method for manufacturing a semiconductor devicein accordance with the present invention includes the step of etchingthe surface of the semiconductor substrate between the step of formingthe abrasive grain marks and the step of placing the doping paste.

Advantageous Effects of Invention

According to the present invention, a semiconductor device and a methodfor manufacturing a semiconductor device capable of stably obtaininggood characteristics can be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic perspective view illustrating one example of thestep of cutting a semiconductor crystal ingot with a wire saw.

FIG. 2 is a schematic perspective view illustrating one example of thestep of cutting the semiconductor crystal ingot at a plurality ofpositions to cut out a plurality of semiconductor substrates.

FIG. 3 is a schematic cross sectional view of one example of the wiresaw shown in FIG. 1.

FIG. 4 is a schematic cross sectional view of one example of asemiconductor substrate obtained by cutting the semiconductor crystalingot with the wire saw shown in FIG. 1.

FIG. 5 is a schematic cross sectional view illustrating one example ofthe step of removing slice damage in surfaces of the semiconductorsubstrate shown in FIG. 4.

FIG. 6 is an enlarged schematic cross sectional view of one example of aportion of a surface of the semiconductor substrate shown in FIG. 5.

FIG. 7 is a schematic perspective view of one example of a portion ofthe surface of the semiconductor substrate shown in FIG. 5.

FIG. 8( a) is a schematic cross sectional view illustrating one exampleof the step of placing an n-type doping paste on a back surface of thesemiconductor substrate, and

FIG. 8( b) is a schematic plan view illustrating one example of the stepof placing the n-type doping paste on the back surface of thesemiconductor substrate.

FIG. 9( a) is a schematic cross sectional view illustrating one exampleof the step of forming an n-type dopant diffusion region in the backsurface of the semiconductor substrate, and FIG. 9( b) is a schematicplan view illustrating one example of the step of forming the n-typedopant diffusion region in the back surface of the semiconductorsubstrate.

FIG. 10( a) is a schematic cross sectional view illustrating one exampleof the step of placing a p-type doping paste on the back surface of thesemiconductor substrate, and FIG. 10( b) is a schematic plan viewillustrating one example of the step of placing the p-type doping pasteon the back surface of the semiconductor substrate.

FIG. 11( a) is a schematic cross sectional view illustrating one exampleof the step of forming a p-type dopant diffusion region in the backsurface of the semiconductor substrate, and FIG. 11( b) is a schematicplan view illustrating one example of the step of forming the p-typedopant diffusion region in the back surface of the semiconductorsubstrate.

FIG. 12( a) is a schematic cross sectional view illustrating one exampleof the step of forming a passivation film on the back surface of thesemiconductor substrate, and FIG. 12( b) is a schematic plan viewillustrating one example of the step of forming the passivation film onthe back surface of the semiconductor substrate.

FIG. 13( a) is a schematic cross sectional view illustrating one exampleof the step of forming a texture structure in a front surface of thesemiconductor substrate, and FIG. 13( b) is a schematic plan viewillustrating one example of the step of forming the texture structure inthe front surface of the semiconductor substrate.

FIG. 14( a) is a schematic cross sectional view illustrating one exampleof the step of forming a passivation film on the front surface of thesemiconductor substrate, and FIG. 14( b) is a schematic plan viewillustrating one example of the step of forming the passivation film onthe front surface of the semiconductor substrate.

FIG. 15( a) is a schematic cross sectional view illustrating one exampleof the step of forming contact holes by removing portions of thepassivation film on the back surface of the semiconductor substrate, andFIG. 15( b) is a schematic plan view illustrating one example of thestep of forming the contact holes by removing portions of thepassivation film on the back surface of the semiconductor substrate.

FIG. 16( a) is a schematic cross sectional view illustrating one exampleof the step of forming an electrode for n type and an electrode for ptype, and FIG. 16( b) is a schematic plan view illustrating one exampleof the step of forming the electrode for n type and the electrode for ptype.

FIG. 17 is a schematic plan view of one example of the n-type dopantdiffusion region and the p-type dopant diffusion region formed in theback surface of the semiconductor substrate.

FIG. 18 is a schematic plan view of another example of the n-type dopantdiffusion region and the p-type dopant diffusion region formed in theback surface of the semiconductor substrate.

FIG. 19 is a schematic plan view of another example of the n-type dopantdiffusion region and the p-type dopant diffusion region formed in theback surface of the semiconductor substrate.

FIG. 20 is an enlarged photograph of a wire saw used in an Example.

FIG. 21 is a microscope photograph of one example of a surface of ann-type single crystal silicon substrate cut with the wire saw shown inFIG. 20.

FIG. 22 is a view showing the result of measuring irregularities of thesurface of the n-type single crystal silicon substrate shown in FIG. 21with a laser microscope.

FIG. 23 is a microscope photograph of another example of the surface ofthe n-type single crystal silicon substrate cut with the wire saw shownin FIG. 22.

FIG. 24 is a view showing the result of measuring irregularities of thesurface of the n-type single crystal silicon substrate shown in FIG. 23with a laser microscope.

FIG. 25 is a microscope photograph of one example of the surface of then-type single crystal silicon substrate shown in FIG. 21 subjected toetching.

FIG. 26 is a view showing the result of measuring irregularities of thesurface of the n-type single crystal silicon substrate shown in FIG. 25with a laser microscope.

FIG. 27 is a view showing the result of measuring irregularities of thesurface of the n-type single crystal silicon substrate shown in FIG. 25subjected to etching with a laser microscope.

FIG. 28( a) is a microscope photograph of the surface of the n-typesingle crystal silicon substrate on which the n-type doping paste isplaced to extend in a direction which forms an angle included in a rangeof −5° to +5° with a direction in which abrasive grain marks extend, andFIG. 28( b) is an enlarged photograph of the microscope photograph ofFIG. 28( a).

FIG. 29( a) is a microscope photograph of the surface of the n-typesingle crystal silicon substrate on which the n-type doping paste isplaced to extend in a direction perpendicular to the direction in whichthe abrasive grain marks extend, and FIG. 29( b) is an enlargedphotograph of the microscope photograph of FIG. 29( a).

FIGS. 30( a) to 30(i) are schematic cross sectional views illustratingone example of a method for manufacturing a conventional back electrodetype solar cell.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a method for manufacturing a back electrode type solar cellin accordance with an embodiment as one example of a method formanufacturing a semiconductor device in accordance with the presentinvention will be described with reference to FIGS. 1 to 16. It is notedthat, in the drawings of the present invention, the same referencenumerals designate identical or corresponding parts.

First, as shown in the schematic perspective view of FIG. 1, the step ofcutting a semiconductor crystal ingot 50 with a wire saw 53 isperformed. As shown in FIG. 1, wire saw 53 are wound on between guiderollers 51, 52 arranged with a predetermined interval therebetween. As aresult, wire saw 53 is tensioned between guide rollers 51, 52, at aplurality of positions in each of guide rollers 51, 52, at predeterminedintervals along a longitudinal direction of guide rollers 51, 52. Inthis state, guide rollers 51, 52 repeat forward rotation and reverserotation, and thereby wire saw 53 reciprocates in a direction indicatedby an arrow 55.

While wire saw 53 is reciprocating in the direction indicated by arrow55, semiconductor crystal ingot 50 is moved in a direction indicated byan arrow 54, and pressed against reciprocating wire saw 53. Thereby, asshown for example in the schematic perspective view of FIG. 2,semiconductor crystal ingot 50 is cut at a plurality of positions, and aplurality of semiconductor substrates 1 are cut out.

FIG. 3 shows a schematic cross sectional view of one example of wire saw53 shown in FIG. 1. Here, wire saw 53 includes a core wire 53 a, andabrasive grains 53 b bonded on an outer peripheral surface of core wire53 a with a bond material (not shown). As core wire 53 a, for example, apiano wire or the like can be used. As abrasive grains 53 b, forexample, diamond abrasive grains or the like can be used. As the bondmaterial, for example, nickel or the like plated on the outer surface ofcore wire 53 a can be used.

FIG. 4 shows a schematic cross sectional view of one example ofsemiconductor substrate 1 obtained by cutting semiconductor crystalingot 50 with wire saw 53. Here, slice damage 1 a is caused in surfacesof semiconductor substrate 1 by cutting semiconductor crystal ingot 50with wire saw 53.

As semiconductor crystal ingot 50, for example, a crystal silicon ingotsuch as a single crystal silicon ingot or a polycrystalline siliconingot fabricated by a Czochralski method or a casting method, or thelike is used. When a crystal silicon ingot is used as semiconductorcrystal ingot 50, a silicon crystal substrate can be obtained assemiconductor substrate 1. It is noted that, in the present embodiment,semiconductor crystal ingot 50 has an n-type conductivity type by beingdoped with an n-type dopant.

Next, as shown in the schematic cross sectional view of FIG. 5, the stepof removing slice damage 1 a in the surfaces of semiconductor substrate1 shown in FIG. 4 is performed. Here, when a silicon crystal substrateis used as semiconductor substrate 1, slice damage 1 a can be removed,for example, by etching with an alkaline aqueous solution such as anaqueous solution of sodium hydroxide or an aqueous solution of potassiumhydroxide.

Although the size and shape of semiconductor substrate 1 are notparticularly limited, for example, a semiconductor substrate having athickness of more than or equal to 100 μm and less than or equal to 300μm, and having a surface in the shape of a rectangle with each sidehaving a length of more than or equal to 100 mm and less than or equalto 200 mm, or the like can be used.

FIG. 6 shows an enlarged schematic cross sectional view of one exampleof a portion of a surface of semiconductor substrate 1 shown in FIG. 5.FIG. 7 shows a schematic perspective view of one example of a portion ofthe surface of semiconductor substrate 1 shown in FIG. 5. Here, in thesurface of semiconductor substrate 1, a large wave (indicated by animaginary dash line in FIG. 6; hereinafter referred to as a “saw mark”)61 is formed, and abrasive grain marks 62 in the shape of groovesshallower than saw mark 61 are formed.

Saw mark 61 is formed resulting from cutting of semiconductor crystalingot 50 with wire saw 53. Specifically, when semiconductor substrate 1is obtained by pressing semiconductor crystal ingot 50 againstreciprocating wire saw 53 and cutting semiconductor crystal ingot 50 asshown in FIG. 1, wire saw 53 is stopped momentarily each time whentraveling direction 55 of wire saw 53 is switched, causing a reductionin the wire speed. This leads to different cutting depths intosemiconductor crystal ingot 50 with wire saw 53 along the direction inwhich semiconductor crystal ingot 50 is moved with respect to wire saw53 (i.e., direction indicated by arrow 54), which appear as saw mark 61that is a large wave in the surface of semiconductor substrate 1.

In addition, abrasive grain marks 62 are flaws formed by abrasive grains53 b of wire saw 53 during cutting of semiconductor crystal ingot 50with wire saw 53, and are formed in the shape of grooves extending intraveling direction 55 of wire saw 53.

It is noted that, although not shown in FIGS. 6 and 7 for convenience ofexplanation, crater-like depressions may be formed in the surface ofsemiconductor substrate 1 by the etching for removing slice damage 1 adescribed above.

Next, as shown in the schematic cross sectional view of FIG. 8( a) andthe schematic plan view of FIG. 8( b), an n-type doping paste 3 isplaced on a portion of a surface on a back side (i.e., back surface) ofsemiconductor substrate 1.

Here, as shown in the schematic plan view of FIG. 8( b), n-type dopingpaste 3 is placed to have a portion extending in a direction which formsan angle included in a range of −5° to +5° with a direction in which theabrasive grain marks (not shown) extend (i.e., direction indicated byarrow 55). This is based on the findings obtained by the inventor of thepresent invention through earnest study that, when n-type doping paste 3is placed to extend in the direction which forms an angle included inthe range of −5° to +5° with the direction in which the abrasive grainmarks extend, n-type doping paste 3 can be suppressed from flowing outin a direction other than the direction in which it extends, whencompared with a case where n-type doping paste 3 is placed to extend ina direction outside the range. Thereby, n-type doping paste 3 can bestably formed, at least in that portion, in the direction which forms anangle included in the range of −5° to +5° with the direction in whichthe abrasive grain marks extend (i.e., direction indicated by arrow 55).It is noted that, the present embodiment will describe a case wheren-type doping paste 3 is formed in the shape of a band extending in adirection which forms an angle of 0° with the direction in which theabrasive grain marks extend (i.e., direction indicated by arrow 55).

As n-type doping paste 3, the one containing an n-type dopant such as aphosphorus compound, and also containing, for example, a solvent, athickener, and a silicon oxide precursor can be used. Further, as n-typedoping paste 3, the one not containing a thickener can also be used.

As the phosphorus compound, for example, a component containingphosphorus atoms such as phosphate, phosphorus oxide, phosphoruspentaoxide, phosphoric acid, or an organic phosphorus compound can beused alone or in combination of two or more kinds thereof.

Examples of the solvent include ethylene glycol, methyl cellosolve,methyl cellosolve acetate, ethyl cellosolve, diethyl cellosolve,cellosolve acetate, ethylene glycol monophenyl ether, methoxyethanol,ethylene glycol monoacetate, ethylene glycol diacetate, diethyleneglycol, diethylene glycol monomethyl ether, diethylene glycol monoethylether acetate, diethylene glycol monobutyl ether, diethylene glycolmonobutyl ether acetate, diethylene glycol dimethyl ether, diethyleneglycol methylethyl ether, diethylene glycol diethyl ether, diethyleneglycol acetate, triethylglycol, triethylene glycol monomethyl ether,triethylene glycol monoethyl ether, tetraethylene glycol, liquidpolyethylene glycol, propylene glycol, propylene glycol monomethylether, propylene glycol monoethyl ether, propylene glycol monobutylether, 1-butoxyethoxy propanol, dipropyl glycol, dipropylene glycolmonomethyl ether, dipropylene glycol monoethyl ether, tripropyleneglycol monomethyl ether, polypropylene glycol, trimethylene glycol,butanedial, 1,5-pentanedial, hexylene glycol, glycerin, glycerylacetate, glycerin diacetate, glyceryl triacetate, trimethylolpropine,1,2,6-hexane triol, 1,2-propanediol, 1,5-pentanedial, octanediol,1,2-butanediol, 1,4-butanediol, 1,3-butanediol, dioxane, trioxane,tetrahydrofuran, tetrahydropyran, methylal, diethyl acetal, methyl ethylketone, methyl isobutyl ketone, diethyl ketone, acetonylacetone,diacetone alcohol, methyl formate, ethyl formate, propyl formate, methylacetate, and ethyl acetate, which can be used alone or in combination oftwo or more kinds thereof.

As the thickener, although it is desirable to use ethyl cellulose,polyvinyl pyrrolidone, or a mixture thereof, it is also possible to usebentonite having various qualities and characteristics, a generallyinorganic rheology additive for various polar solvent mixtures,nitrocellulose and other cellulose compounds, starch, gelatin, alginicacid, highly-dispersive amorphous silicic acid (Aerosil (registeredtrademark)), polyvinyl butyral (Mowital (registered trademark)), sodiumcarboxymethyl cellulose (vivistar), thermoplastic polyimide resin(Eurelon (registered trademark)), an organic castor oil derivative(Thixin R (registered trademark)), diamide wax (Thixatrol plus(registered trademark)), swelable polyacrylate (Rheolate (registeredtrademark)), polyether urea-polyurethane, polyether-polyol, or the like.

As the silicon oxide precursor, for example, a substance represented bya general formula R¹′nSi(OR¹)_(4-n), (where R¹′ represents methyl,ethyl, or phenyl, R¹ represents methyl, ethyl, n-propyl, or i-propyl,and n represents 0, 1, or 2) such as TEOS (tetraethyl orthosilicate) canbe used.

N-type doping paste 3 can be placed, for example, using a conventionallyknown technique such as screen printing, inkjet printing, or the like.

Thereafter, n-type doping paste 3 placed on the back surface ofsemiconductor substrate 1 is dried.

N-type doping paste 3 can be dried, for example, by placingsemiconductor substrate 1 having the paste placed thereon inside anoven, and heating the paste at a temperature of, for example, about 200°C. for a period of, for example, several tens of minutes.

Next, as shown in the schematic cross sectional view of FIG. 9( a) andthe schematic plan view of FIG. 9( b), semiconductor substrate 1 is putinto a quartz furnace at more than or equal to 800° C. and less than orequal to 1100° C. to diffuse the n-type dopant from n-type doping paste3 into the back surface of semiconductor substrate 1, to form an n-typedopant diffusion region 13. Thereby, as shown in the schematic plan viewof FIG. 9( b), n-type dopant diffusion region 13 is formed in the shapeof a band extending in a direction which forms an angle included in therange of −5° to +5° with the direction in which the abrasive grain marksextend (i.e., direction indicated by arrow 55). It is noted that n-typedopant diffusion region 13 is a region having an n- type dopantconcentration higher than that in semiconductor substrate 1.

Thereafter, a residue of n-type doping paste 3 on the back surface ofsilicon substrate 1 is removed. The residue of n-type doping paste 3 canbe removed, for example, by immersing semiconductor substrate 1 havingn-type doping paste 3 placed thereon in an aqueous solution ofhydrofluoric acid, or the like.

Next, as shown in the schematic cross sectional view of FIG. 10( a) andthe schematic plan view of FIG. 10( b), a p-type doping paste 4 isplaced on a portion of the back surface of semiconductor substrate 1.

Here, as shown in the schematic plan view of FIG. 10( b), p-type dopingpaste 4 is placed to have a portion extending in a direction which formsan angle included in a range of −5° to +5° with the direction in whichthe abrasive grain marks (not shown) extend (i.e., direction indicatedby arrow 55), as with n-type doping paste 3 described above.

As p-type doping paste 4, the one containing a p-type dopant such as aboron compound, and also containing, for example, a solvent, athickener, and a silicon oxide precursor can be used. Further, as p-typedoping paste 4, the one not containing a thickener can also be used.

As the boron compound, for example, a compound containing boron atomssuch as boron oxide, boric acid, an organic boron compound, or aboron-aluminum compound can be used alone or in combination of two ormore kinds thereof.

As the solvent, the same solvent as that in n-type doping paste 3described above can be used.

As the thickener, the same thickener as that in n-type doping paste 3described above can be used.

As the silicon oxide precursor, the same substance as that in n-typedoping paste 3 described above can be used.

P-type doping paste 4 can be placed using the same technique as that forplacing n-type doping paste 3 described above.

Thereafter, p-type doping paste 4 placed on the back surface ofsemiconductor substrate 1 is dried.

P-type doping paste 4 can be dried using the same technique as that fordrying n-type doping paste 3 described above.

Next, as shown in the schematic cross sectional view of FIG. 11( a) andthe schematic plan view of FIG. 11( b), semiconductor substrate 1 is putinto the quartz furnace at more than or equal to 800° C. and less thanor equal to 1100° C. to diffuse the p-type dopant from p-type dopingpaste 4 into the back surface of semiconductor substrate 1, to form ap-type dopant diffusion region 14. Thereby, as shown in the schematicplan view of FIG. 11( b), p-type dopant diffusion region 14 is formed inthe shape of a band extending in a direction which forms an angleincluded in the range of −5° to +5° with the direction in which theabrasive grain marks extend (i.e., direction indicated by arrow 55).

Thereafter, a residue of p-type doping paste 4 on the back surface ofsilicon substrate 1 is removed. The residue of p-type doping paste 4 canbe removed, for example, by immersing semiconductor substrate 1 havingp-type doping paste 4 placed thereon in an aqueous solution ofhydrofluoric acid, or the like.

Next, as shown in the schematic cross sectional view of FIG. 12( a) andthe schematic plan view of FIG. 12( b), a passivation film 5 is formedon the back surface of semiconductor substrate 1. As passivation film 5,for example, a silicon nitride film, a silicon oxide film, a laminatedfilm of a silicon nitride film and a silicon oxide film, or the like canbe used. Passivation film 5 can be formed, for example, by a plasma CVDmethod or the like.

Next, as shown in the schematic cross sectional view of FIG. 13( a), atexture structure 10 is formed by texture-etching a light receivingsurface of semiconductor substrate 1 which is on a side opposite to aside having passivation film 5 formed thereon. The texture-etching forforming texture structure 10 can be performed by using passivation film5 formed on the other surface of semiconductor substrate 1 as an etchingmask. When semiconductor substrate 1 is made of a silicon crystalsubstrate, the texture-etching can be performed by etching the lightreceiving surface of semiconductor substrate 1 with an etching solutionprepared for example by adding isopropyl alcohol to an aqueous solutionof alkali such as sodium hydroxide or potassium hydroxide and heatingthe solution to, for example, more than or equal to 70° and less than orequal to 80° C.

Next, as shown in the schematic cross sectional view of FIG. 14( a), apassivation film 6 is formed on the light receiving surface ofsemiconductor substrate 1. As passivation film 6, for example, a siliconnitride film, a silicon oxide film, a laminated film of a siliconnitride film and a silicon oxide film, or the like can be used.Passivation film 6 can be formed, for example, by the plasma CVD methodor the like. Further, passivation film 6 on the light receiving surfaceof semiconductor substrate 1 is a film also serving as a so-calledantireflection film.

Next, as shown in the schematic cross sectional view of FIG. 15( a) andthe schematic plan view of FIG. 15( b), a contact hole 23 and a contacthole 24 are formed by removing portions of passivation film 5 on theback surface of semiconductor substrate 1 to expose a portion of n-typedopant diffusion region 13 from contact hole 23 and expose a portion ofp-type dopant diffusion region 14 from contact hole 24.

Contact holes 23, 24 can be formed, for example, by a method of forminga resist pattern having openings at portions corresponding to positionswhere contact holes 23, 24 are to be formed, on passivation film 5 usinga photolithographic technique, and thereafter removing passivation film5 from the openings in the resist pattern by etching.

Next, as shown in the schematic cross sectional view of FIG. 16( a) andthe schematic plan view of FIG. 16( b), an electrode for n type 33electrically connected to n-type dopant diffusion region 13 throughcontact hole 23 is formed, and an electrode for p type 34 electricallyconnected to p-type dopant diffusion region 14 through contact hole 24is formed. Here, as electrode for n type 33 and electrode for p type 34,for example, an electrode made of a metal such as silver can be used.Thus, the back electrode type solar cell in the present embodiment canbe fabricated.

As described above, in the present embodiment, since n-type doping paste3 and p-type doping paste 4 are each placed to have a portion extendingin the direction which forms an angle included in the range of −5° to+5° with the direction in which the abrasive grain marks extend asdescribed above, n-type doping paste 3 and p-type doping paste 4 can beeach formed to have a stable shape, at least in that portion, in thedirection which forms an angle included in the range of −5° to +5° withthe direction in which the abrasive grain marks extend.

Thereby, in the present embodiment, n-type dopant diffusion region 13and p-type dopant diffusion region 14 can also be each formed stably ina desired shape, and thus the back electrode type solar cell can havegood characteristics stably.

It is noted that, although the above embodiment has described asemiconductor crystal ingot having an n-type conductivity type, thesemiconductor crystal ingot may have a p-type conductivity type.

Further, n-type dopant diffusion region 13 and p-type dopant diffusionregion 14 may each have a shape extending in one direction, as shown inthe schematic plan view of FIG. 17. Alternatively, a portion of at leastone of n-type dopant diffusion region 13 and p-type dopant diffusionregion 14 may be perpendicular to the direction in which the abrasivegrain marks extend, as shown in the schematic plan view of FIG. 18.Alternatively, only either n-type dopant diffusion region 13 or p-typedopant diffusion region 14 may have a shape extending in one direction,as shown in the schematic plan view of FIG. 19.

Furthermore, the present invention is not limited to a back electrodetype solar cell, and is also applicable to semiconductor devicesincluding a solar cell of any configuration such as a bifacial electrodetype solar cell manufactured by forming electrodes on both a lightreceiving surface and a back surface of a semiconductor substrate.

EXAMPLE

Placement of Doping Paste

First, an n-type single crystal silicon ingot was pressed against areciprocating wire saw (having a shape shown in the enlarged photographof FIG. 20) and cut. Thereby, a plurality of n-type single crystalsilicon substrates each having a thickness of 200 μm were formed, inwhich abrasive grain marks in the shape of grooves extending in onedirection were formed in a light receiving surface and a back surface inthe shape of a quasi square with each side having a length of 126 mm.The wire saw shown in FIG. 20 used herein was fabricated by bondingdiamond abrasive grains having a grain size of less than or equal to 30μm, on an outer peripheral surface of a piano wire having a crosssectional diameter of 120 μm, with nickel plated thereon.

FIG. 21 shows a microscope photograph of one example of a surface of ann-type single crystal silicon substrate cut with the wire saw describedabove, and FIG. 22 shows the result of measuring irregularities of thesurface of the n-type single crystal silicon substrate shown in FIG. 21with a laser microscope. It is noted that the axis of abscissas in FIG.22 represents the width of the surface of the n-type single crystalsilicon substrate (maximum width: 10 mm), and the axis of ordinates inFIG. 22 represents irregularities of the surface of the n-type singlecrystal silicon substrate caused by a saw mark and abrasive grain marksresulting from cutting with the wire saw.

FIG. 23 shows a microscope photograph of another example of the surfaceof the n-type single crystal silicon substrate cut with the wire sawdescribed above, and FIG. 24 shows the result of measuringirregularities of the surface of the n-type single crystal siliconsubstrate shown in FIG. 23 with a laser microscope. It is noted that theaxis of abscissas in FIG. 24 represents the width of the surface of then-type single crystal silicon substrate (maximum width: 10 mm), and theaxis of ordinates in FIG. 24 represents irregularities of the surface ofthe n-type single crystal silicon substrate caused by a saw mark andabrasive grain marks resulting from cutting with the wire saw.

It was confirmed that, as shown in FIGS. 21 to 24, a saw mark as a largewave formed along a direction in which the n-type single crystal siliconingot was pressed against the wire saw, and abrasive grain marks in theshape of grooves formed in the saw mark along a traveling direction ofthe wire saw (vertical lines in FIGS. 21 and 23) were formed in thesurface of the n-type single crystal silicon substrate.

Next, slice damage in the surface of the n-type single crystal siliconsubstrate was removed by etching the surface of the n-type singlecrystal silicon substrate formed as described above, to a depth of 30μm, with an aqueous solution of sodium hydroxide having a sodiumhydroxide concentration of 48% by mass (i.e., 48 g of sodium hydroxidewith respect to 52 g of water).

FIG. 25 shows a microscope photograph of one example of the surface ofthe n-type single crystal silicon substrate shown in FIG. 21 subjectedto etching, and FIG. 26 shows the result of measuring irregularities ofthe surface of the n-type single crystal silicon substrate shown in FIG.25 with a laser microscope. FIG. 27 shows the result of measuringirregularities of the surface of the n-type single crystal siliconsubstrate shown in FIG. 25 subjected to etching with a laser microscope.Although circular depressions were formed in the surface of the n-typesingle crystal silicon substrate as shown in FIG. 25, the abrasive grainmarks did not disappear from the surface of the n-type single crystalsilicon substrate as shown in FIGS. 26 and 27.

Next, on the surface of the n-type single crystal silicon substratesubjected to etching described above, an n-type doping paste in theshape of a plurality of bands (design width of one band of the n-typedoping paste: 300 μm, viscosity: 30 Pa·s) was placed intermittently atan interval of 1.5 mm to extend in a direction which formed an angleincluded in a range of −5° to +5° with a direction in which the abrasivegrain marks extended.

FIG. 28( a) shows a microscope photograph of the surface of the n-typesingle crystal silicon substrate on which the n-type doping paste isplaced to extend in the direction which forms an angle included in therange of −5° to +5° with the direction in which the abrasive grain marksextend, and FIG. 28( b) shows an enlarged photograph of the microscopephotograph of FIG. 28( a). In FIGS. 28( a) and 28(b), a dark-coloredportion is where the n-type doping paste is placed, and a light-coloredportion indicates an opening.

It was confirmed that, as shown in FIGS. 28( a) and 28(b), when then-type doping paste was placed to extend in the direction which formedan angle included in the range of −5° to +5° with the direction in whichthe abrasive grain marks extended, the n-type doping paste was able tobe suppressed from flowing out in a direction other than the directionin which the n-type doping paste extended.

As a Comparative Example, the n-type doping paste was placed asdescribed above, except for placing the n-type doping paste in the shapeof a plurality of bands to extend in a direction perpendicular to thedirection in which the abrasive grain marks extended.

FIG. 29( a) shows a microscope photograph of the surface of the n-typesingle crystal silicon substrate on which the n-type doping paste isplaced to extend in the direction perpendicular to the direction inwhich the abrasive grain marks extend, and FIG. 29( b) shows an enlargedphotograph of the microscope photograph of FIG. 29( a). In FIGS. 29( a)and 29(b), a dark-colored portion is where the n-type doping paste isplaced, and a light-colored portion indicates an opening.

It was confirmed that, as shown in FIGS. 29( a) and 29(b), when then-type doping paste was placed to extend in the direction perpendicularto the direction in which the abrasive grain marks extended, the n-typedoping paste flew out in a direction other than the direction in whichthe n-type doping paste extended, and had a varied width, when comparedwith the case where the n-type doping paste was placed to extend in thedirection which formed an angle included in the range of −5° to +5° withthe direction in which the abrasive grain marks extended.

Further, from the surface of the n-type single crystal silicon substrateon which the n-type doping paste was placed to extend in the directionwhich formed an angle included in the range of −5° to +5° with thedirection in which the abrasive grain marks extended, any 10 n-typedoping paste-placed portions (sample Nos. 1 to 10) were selected, themaximum value and the minimum value of the width of each of these 10n-type doping paste-placed portions were measured, and the differencebetween the maximum value and the minimum value was calculated. Then, anaverage value and a standard deviation σ were calculated for each of themaximum values, the minimum values, and the differences between themaximum values and the minimum values, of the widths of the n-typedoping paste-placed portions of sample Nos. 1 to 10. Table 1 showsresults thereof.

TABLE 1 Sample No. Maximum Width Minimum Width Maximum Width − MinimumWidth  1 333 292 41  2 356 303 53  3 320 289 31  4 344 295 49  5 306 28026  6 328 291 37  7 317 275 42  8 321 290 31  9 332 292 40 10 310 298 12Average Value 327 291 36 σ 15 8 12 (n-type doping paste appliedvertically*1) *1the n-type doping paste was placed to extend in thedirection which formed an angle included in the range of −5° to +5° withthe direction in which the abrasive grain marks extended (unit: μm)

As shown in Table 1, for the maximum values, the minimum values, and thedifferences between the maximum values and the minimum values of thewidths of the n-type doping paste-placed portions of sample Nos. 1 to10, the average values were 327, 291, and 36, respectively, and standarddeviations σ were 15, 8, and 12, respectively.

In contrast, from the surface of the n-type single crystal siliconsubstrate on which the n-type doping paste was placed to extend in thedirection perpendicular to the direction in which the abrasive grainmarks extended, any 10 n-type doping paste-placed portions wereselected, the maximum value and the minimum value of the width of eachof these 10 n-type doping paste-placed portions (sample Nos. 11 to 20)were measured, and the difference between the maximum value and theminimum value was calculated. Then, an average value and standarddeviation σ were calculated for each of the maximum values, the minimumvalues, and the differences between the maximum values and the minimumvalues, of the widths of the n-type doping paste-placed portions ofsample Nos. 11 to 20. Table 2 shows results thereof.

TABLE 2 Sample No. Maximum Width Minimum Width Maximum Width − MinimumWidth 11 381 300 81 12 356 288 68 13 375 293 82 14 374 290 84 15 396 275121 16 428 305 123 17 396 292 104 18 361 292 69 19 388 294 94 20 403 303100 Average Value 386 293 93 σ 21 9 19 (n-type doping paste appliedlaterally*2) *2the doping paste was placed to extend in the directionperpendicular to the direction in which the abrasive grain marksextended (unit: μm)

As shown in Table 2, for the maximum values, the minimum values, and thedifferences between the maximum values and the minimum values of thewidths of the n-type doping paste-placed portions of sample Nos. 11 to20, the average values were 386, 293, 93, respectively, and standarddeviations σ were 21, 9, and 19, respectively.

Similarly, for a p-type doping paste, comparison was made between a casewhere the p-type doping paste was placed to extend in a direction whichformed an angle included in a range of −5° to +5° with the direction inwhich the abrasive grain marks extended and a case where the p-typedoping paste was placed to extend in a direction perpendicular to thedirection in which the abrasive grain marks extended. The p-type dopingpaste in the shape of a plurality of bands was placed on the surface ofthe silicon substrate, intermittently at an interval of 1.5 mm (designwidth of one band of the p-type doping paste: 1000 μm, viscosity: 30Pa·s)

As with the n-type doping paste, from the surface of the n-type singlecrystal silicon substrate on which the p-type doping paste was placed toextend in the direction which formed an angle included in the range of−5° to +5° with the direction in which the abrasive grain marksextended, any 10 p-type doping paste-placed portions (sample Nos. 21 to30) were selected, the maximum value and the minimum value of the widthof each of these 10 p-type doping paste-placed portions were measured,and the difference between the maximum value and the minimum value wascalculated. Table 3 shows results thereof.

Further, as the Comparative Example, from the surface of the n-typesingle crystal silicon substrate on which the p-type doping paste wasplaced to extend in a direction perpendicular to the direction in whichthe abrasive grain marks extended, any 10 p-type doping paste-placedportions were selected, the maximum value and the minimum value of thewidth of each of these 10 p-type doping paste-placed portions (sampleNos. 31 to 40) were measured, and the difference between the maximumvalue and the minimum value was calculated. Table 4 shows resultsthereof.

Furthermore, an average value and standard deviation σ were calculatedfor each of the maximum values, the minimum values, and the differencesbetween the maximum values and the minimum values, of the widths of thep-type doping paste-placed portions of sample Nos. 21 to 30 and sampleNos. 31 to 40. Tables 3 and 4 show results thereof.

TABLE 3 Sample No. Maximum Width Minimum Width Maximum Width − MinimumWidth 21 1028 980 48 22 1009 967 42 23 1036 992 44 24 1020 970 50 251036 985 51 26 1031 992 39 27 1042 1001 41 28 1015 979 36 29 1029 977 5230 1045 995 50 Average Value 1029 974 45 σ 12 11 6 (p-type doping pasteapplied vertically*1) *1the p-type doping paste was placed to extend inthe direction which formed an angle included in the range of −5° to +5°with the direction in which the abrasive grain marks extended (unit: μm)

TABLE 4 Sample No. Maximum Width Minimum Width Maximum Width − MinimumWidth 31 1088 977 111 32 1112 989 123 33 1140 991 149 34 1095 964 131 351124 997 127 36 1108 993 115 37 1099 981 118 38 1131 993 138 39 11541005 149 40 1129 980 149 Average Value 1118 987 131 σ 21 12 15 (p-typedoping paste applied laterally*2) *2the doping paste was placed toextend in the direction perpendicular to the direction in which theabrasive grain marks extended (unit: μm)

As shown in Table 3, for the maximum values, the minimum values, and thedifferences between the maximum values and the minimum values of thewidths of the p-type doping paste-placed portions of sample Nos. 21 to30, the average values were 1029, 974, and 45, respectively, andstandard deviations σ were 12, 11, and 6, respectively.

Further, as shown in Table 4, for the maximum values, the minimumvalues, and the differences between the maximum values and the minimumvalues of the widths of the p-type doping paste-placed portions ofsample Nos. 31 to 40, the average values were 1118, 987, and 131,respectively, and standard deviations σ were 21, 12, and 15,respectively.

As described above, it was confirmed that, as shown in Tables 1 to 4,deviation of the width of the n-type doping paste from a designed valuecan be suppressed when the doping paste is placed to extend in thedirection which forms an angle included in the range of −5° to +5° withthe direction in which the abrasive grain marks extend, when comparedwith the case where the doping paste is placed to extend in thedirection perpendicular to the direction in which the abrasive grainmarks extend.

Fabrication and Evaluation of Back Electrode Type Solar Cell

Back electrode type solar cells were fabricated, respectively using ann-type single crystal silicon substrate having n-type dopingpaste-placed portions of sample Nos. 1 to 10 and p-type dopingpaste-placed portions of sample Nos. 21 to 30 (i.e., a substrate of theExample), and an n-type single crystal silicon substrate having n-typedoping paste-placed portions of sample Nos. 11 to 20 and p-type dopingpaste-placed portions of sample Nos. 31 to 40 (i.e., a substrate of theComparative Example).

Specifically, first, an n-type doping paste was placed on each of thesubstrates of the Example and the Comparative Example thermally oxidizedin a quartz furnace at 900° C. for 20 minutes in an oxygen atmosphere.Thereafter, each of the substrates of the Example and the ComparativeExample was placed inside an oven and heated at 200° C. for 30 minutesto dry the n-type doping paste.

Next, each of the substrates of the Example and the Comparative Examplewas heated in the quartz furnace at 950° C. for 30 minutes, and therebyphosphorus was diffused at the n-type doping paste-placed portions ineach of the substrates of the Example and the Comparative Example toform n-type dopant diffusion regions.

Next, each of the substrates of the Example and the Comparative Examplewas immersed in an aqueous solution of hydrofluoric acid, therebyremoving all of the residue of the n-type doping paste on each of thesubstrates of the Example and the Comparative Example.

Next, a p-type doping paste was placed between the n-type dopantdiffusion regions formed in each of the substrates of the Example andthe Comparative Example thermally oxidized in the quartz furnace at 900°C. for 20 minutes in an oxygen atmosphere. Thereafter, each of thesubstrates of the Example and the Comparative Example was placed insidethe oven and heated at 200° C. for 30 minutes to dry the p-type dopingpaste.

Next, each of the substrates of the Example and the Comparative Examplewas heated in the quartz furnace at 1000° C. for 30 minutes, and therebyboron was diffused at the p-type doping paste-placed portions in each ofthe substrates of the Example and the Comparative Example to form p-typedopant diffusion regions.

Next, each of the substrates of the Example and the Comparative Examplewas immersed in an aqueous solution of hydrofluoric acid, therebyremoving all of the residue of the p-type doping paste on each of thesubstrates of the Example and the Comparative Example.

Next, a passivation film made of a silicon nitride film was formed bythe plasma CVD method over the entire surface of each of the substratesof the Example and the Comparative Example on a side where the n-typedopant diffusion regions and the p-type dopant diffusion regions wereformed.

Next, a texture structure was formed by texture-etching a surface ofeach of the substrates of the Example and the Comparative Example on aside opposite to the side having the passivation film formed thereon.Here, the texture-etching was performed using an etching solution at 70°C. to 80° C. prepared by adding isopropyl alcohol to an aqueous solutionof sodium hydroxide having a sodium hydroxide concentration of 3% bymass.

Next, an antireflection film made of a silicon nitride film was formedby the plasma CVD method on the texture structure of each of thesubstrates of the Example and the Comparative Example.

Next, contact holes were formed by removing portions of the passivationfilm on each of the substrates of the Example and the ComparativeExample in the shape of bands to expose a portion of each of the n-typedopant diffusion regions and the p-type dopant diffusion regions.

Thereafter, a commercially available silver paste was applied to fillthe contact holes in each of the substrates of the Example and theComparative Example, was dried, and fired by being heated at 600° C. for20 minutes, to form silver electrodes in contact with the n-type dopantdiffusion regions and the p-type dopant diffusion regions, respectively.Thereby, the back electrode type solar cells respectively using thesubstrates of the Example and the Comparative Example were fabricated.

Subsequently, each of the back electrode type solar cell fabricatedusing the substrate of the Example (i.e., solar cell of the Example) andthe back electrode type solar cell fabricated using the substrate of theComparative Example (i.e., solar cell of the Comparative Example) wasirradiated with quasi solar light using a solar simulator, andcurrent-voltage (IV) characteristics were measured, and short circuitcurrent density, open voltage, F. F (Fill Factor), conversionefficiency, and leak current were measured. Table 5 shows resultsthereof. It is noted that, in Table 5, values of the short circuitcurrent density, open voltage, F. F, conversion efficiency, and leakcurrent of the solar cell of the Example are expressed as relativevalues obtained when values of the short circuit current density, openvoltage, F. F, conversion efficiency, and leak current of the solar cellof the Comparative Example are each set to 100.

TABLE 5 Short Circuit Open Conversion Leak Current Density Voltage F. FEfficiency Current Example 104 101 109 115  9 Comparative 100 100 100100 100 Example

It was confirmed that, as shown in Table 5, the solar cell of theExample has higher short circuit current density, open voltage, F. F,conversion efficiency, and lower leak current, when compared with thesolar cell of the Comparative Example. Therefore, the solar cell of theExample can stably obtain good characteristics, when compared with thesolar cell of the Comparative Example.

This is considered to be because, since the n-type dopant diffusionregions and the p-type dopant diffusion regions can be stably formed inthe shape of bands extending in the direction which forms an angleincluded in the range of −5° to +5° with the direction in which theabrasive grain marks extend in the solar cell of the Example, each ofthe n-type dopant diffusion regions and the p-type dopant diffusionregions has less variation in width, when compared with the solar cellof the Comparative Example.

It should be understood that the embodiment and the example disclosedherein are illustrative and non-restrictive in every respect. The scopeof the present invention is defined by the scope of the claims, ratherthan the description above, and is intended to include any modificationswithin the scope and meaning equivalent to the scope of the claims.

Industrial Applicability

The present invention is applicable to a semiconductor device and amethod for manufacturing a semiconductor device, and in particularsuitably applicable to a back electrode type solar cell and a method formanufacturing a back electrode type solar cell.

Reference Signs List

1: semiconductor substrate; 1 a: slice damage; 3: n-type doping paste;4: p-type doping paste; 5: passivation film; 10: texture structure; 6:passivation film; 13: n-type dopant diffusion region; 14: p-type dopantdiffusion region; 23, 24: contact hole; 33: electrode for n type; 34:electrode for p type; 50: semiconductor crystal ingot; 51, 52: guideroller; 53: wire saw; 53 a: core wire; 53 b: abrasive grains; 54, 55:arrow; 61: saw mark; 62: abrasive grain marks; 101: silicon substrate;103: n-type doping paste; 104: p-type doping paste; 105: silicon oxidefilm; 106: light receiving surface passivation film; 110: texturestructure; 113: n-type dopant diffusion region; 114: p-type dopantdiffusion region; 123, 124: contact hole; 133: electrode for n type;134: electrode for p type.

1. A semiconductor device, comprising: a semiconductor substrate; and adopant diffusion region provided in one surface of said semiconductorsubstrate, wherein abrasive grain marks are formed in said surface ofsaid semiconductor substrate, said dopant diffusion region has a portionextending in a direction which forms an angle included in a range of −5°to +5° with a direction in which said abrasive grain marks extend, andsaid dopant diffusion region is formed by diffusing a dopant from adoping paste placed on the one surface of said semiconductor substrate.2. The semiconductor device according to claim 1, wherein said dopantdiffusion region has at least one of an n-type dopant diffusion regionand a p-type dopant diffusion region, and the semiconductor devicefurther comprises: an electrode for n type provided on said n-typedopant diffusion region; and an electrode for p type provided on saidp-type dopant diffusion region.
 3. A method for manufacturing asemiconductor device, comprising the steps of: forming abrasive grainmarks extending in one direction in a surface of a semiconductorsubstrate; placing a doping paste having a portion extending in adirection which forms an angle included in a range of −5° to +5° with adirection in which said abrasive grain marks extend, on a portion ofsaid surface of said semiconductor substrate; and forming a dopantdiffusion region from a dopant in said doping paste on saidsemiconductor substrate.
 4. The method for manufacturing a semiconductordevice according to claim 3, wherein said step of forming the abrasivegrain marks includes the step of cutting a semiconductor crystal ingotwith a wire saw.
 5. The method for manufacturing a semiconductor deviceaccording to claim 3, comprising the step of etching said surface ofsaid semiconductor substrate between said step of forming the abrasivegrain marks and said step of placing the doping paste.